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参数资料
| 型号： | DS1251YP |
| 英文描述： | 4096k NV SRAM with Phantom Clock |
| 中文描述： | 4096k非易失SRAM与幻影时钟 |
| 文件页数： | 3/22页 |
| 文件大小： | 291K |
| 代理商： | DS1251YP |
DS1251/DS1251P
3 of 22
RAM READ MODE
The DS1251 executes a read cycle whenever
WE
(write enable) is inactive (high) and
CE
(chip enable) is
active (low). The unique address specified by the 19 address inputs (A0–A18) defines which of the 512k
bytes of data is to be accessed. Valid data will be available to the eight data-output drivers within t
ACC
(access time) after the last address input signal is stable, providing that
CE
and
OE
(output enable) access
times and states are also satisfied. If
OE
and
CE
access times are not satisfied, then data access must be
measured from the later occurring signal (
CE
or
OE
) and the limiting parameter is either t
CO
for
CE
or
t
OE
for
OE
, rather than address access.
RAM WRITE MODE
The DS1251 is in the write mode whenever the
WE
and
CE
signals are in the active (low) state after
address inputs are stable. The latter occurring falling edge of
CE
or
WE
will determine the start of the
write cycle. The write cycle is terminated by the earlier rising edge of
CE
or
WE
. All address inputs must
be kept valid throughout the write cycle.
WE
must return to the high state for a minimum recovery time
(t
WR
) before another cycle can be initiated. The
OE
control signal should be kept inactive (high) during
write cycles to avoid bus contention. However, if the output bus has been enabled (
CE
and
OE
active)
then
WE
will disable the outputs in t
ODW
from its falling edge.
DATA RETENTION MODE
The 5V device is fully accessible and data can be written or read only when V
CC
is greater than V
PF
.
However, when V
CC
is below the power-fail point, V
PF
(point at which write protection occurs), the
internal clock registers and SRAM are blocked from any access. When V
CC
falls below the battery switch
point, V
SO
(battery supply level), device power is switched from the V
CC
pin to the backup battery. RTC
operation and SRAM data are maintained from the battery until V
CC
is returned to nominal levels.
The 3.3V device is fully accessible and data can be written or read only when V
CC
is greater than V
PF.
When V
CC
falls below the power-fail point, V
PF
, access to the device is inhibited. If V
PF
is less than V
BAT,
the device power is switched from V
CC
to the backup supply (V
BAT
) when V
CC
drops below V
PF
. If V
PF
is
greater than V
BAT
, the device power is switched from V
CC
to the backup supply (V
BAT
) when V
CC
drops
below V
BAT
. RTC operation and SRAM data are maintained from the battery until V
CC
is returned to
nominal levels.
All control, data, and address signals must be powered down when V
CC
is powered down.
PHANTOM CLOCK OPERATION
Communication with the phantom clock is established by pattern recognition on a serial bit stream of
64 bits, which must be matched by executing 64 consecutive write cycles containing the proper data on
DQ0. All accesses that occur prior to recognition of the 64-bit pattern are directed to memory.
After recognition is established, the next 64 read or write cycles either extract or update data in the
phantom clock, and memory access is inhibited.
Data transfer to and from the timekeeping function is accomplished with a serial bit stream under control
of chip enable, output enable, and write enable. Initially, a read cycle to any memory location using the
相关PDF资料 |
PDF描述 |
|---|---|
| DS1258Y-70 | 128k x 16 Nonvolatile SRAM |
| DS1258Y-70-IND | Safety Sign; Legend:Notice Authorized Personnel Only; External Height:7"; External Width:10"; Body Material:Polyester; Color:Blue/Black RoHS Compliant: NA |
| DS1258W-100 | 3.3V 128k x 16 Nonvolatile |
| DS1258W-150 | 3.3V 128k x 16 Nonvolatile |
| DS1258WP-100 | 3.3V 128k x 16 Nonvolatile |
相关代理商/技术参数 |
参数描述 |
|---|---|
| DS1251YP/WP | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:PowerCap with Crystal |
| DS1251YP-100 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| DS1251YP-70 | 功能描述:实时时钟 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
| DS1251YP-70+ | 功能描述:实时时钟 4096K NV SRAM w/Phantom Clock RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
| DS1251YP-70IND | 功能描述:实时时钟 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 总线接口:I2C 日期格式:DW:DM:M:Y 时间格式:HH:MM:SS RTC 存储容量:64 B 电源电压-最大:5.5 V 电源电压-最小:1.8 V 最大工作温度:+ 85 C 最小工作温度: 安装风格:Through Hole 封装 / 箱体:PDIP-8 封装:Tube |
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